The invention relates to core making machines of the type wherein a blow head is used to direct sand in a pressurized gaseous carrier medium into a core box by way of a blow plate. More particularly, the invention relates to improvements in core making machines of the type disclosed, for example, in U.S. Pat. No. 2,705,821 to Peterson.
It is known to supply a core making machine with a set of different blow plates wherein the openings are distributed in a manner to ensure proper introduction of molding sand into selected core boxes. A foundry normally employs hundreds of different core boxes and blow plates, and the core making machine is provided with means for separably connecting its blow head with a selected blow plate. Such connecting means normally includes screws which secure the marginal portion of a selected blow plate to the adjacent portion of the blow head. The unit including the blow head and the selected blow plate, which is affixed to the blow head, is thereupon attached to a so-called sand head or to any other suitable device which supplies to the blow head at least one stream of sand in a gaseous carrier medium for admission into a core box by way of one or more openings in the selected blow plate. As a rule, the interval of time which is required to replace a blow plate with a different blow plate is between 10 and 40 minutes, depending on the size of the blow head and blow plate and on the number and nature of devices which are used to separably attach the blow plate to the blow head. Thus, each and every replacement of a blow plate entails a prolonged interruption of operation of the core making machine with attendant losses in output. The situation is aggravated if the fasteners which are used to separably connect the blow head with a selected blow plate and/or the fasteners which are used to separably connect the blow head to the means for supplying molding sand become contaminated or corroded by sand and/or as a result of exposure to moisture so that they cannot be readily detached or reapplied. This further prolongs the intervals of idleness of the core making machine. Still further, the connection between the blow head and a selected blow plate as well as the connection between the blow head and its carrier (such as a sand head) is likely to develop leaks in response to repeated attachment and detachment of the blow head from the carrier and/or a blow plate; this entails uncontrolled escape of conveyed sand with the pressurized gaseous carrier medium and improper filling of a core box and/or contamination of the area around the machine. The threads of screws or similar fasteners, as well as the threads in tapped bores for the shanks of such threaded fasteners, are likely to be damaged or destroyed in response to repeated separation and reattachment of the blow head so that the blow head can become completely separated from its carrier or a selected blow plate can become completely detached from the blow head while the machine is in actual use.
German Pats. Nos. 972,225 (to Hansberg) and 1,177,291 (to Bachmann et al.) disclose core making machines wherein the manner of connecting blow plates to the blow head is not described and/or shown. It is assumed that the connections are separable.
German Pat. No. 930,104 to Hansberg discloses a core making machine wherein a selected blow plate can be separably connected to the blow head by a set of screws. This also applies for the connection of a selected blow plate to the blow head in the core making machine which is disclosed by Peterson.
As a rule, the blow head of a core making machine is a one-piece body (reference may be had, for example, to Bachmann et al. and Hansberg '104). This is considered to be desirable and necessary in order to reduce the number of parts as well as to reduce the likelihood of penetration and entrapment of sand between separable components. The discharge end of the sand head is directly adjacent the one-piece blow head. Such sand head can be removed only when the blow head is detached from its carrier, for example, a tubular housing for the sand head. The means for separably connecting the blow head to the carrier normally includes a set of screws. Since the replacement of a previously used blow plate with a different blow plate often necessitates the utilization of a different blow head as well as the utilization of a different sand head, each such change of setup involves a separation of the blow plate from the blow head which is installed in the core making machine, separation of the blow head from its carrier, removal of the sand head, insertion of a different sand head, attachment of a different blow head to the freshly inserted sand head, and attachment of a different blow plate to the freshly installed blow head. The reason that it is often necessary to replace a blow head with a different blow head and to simultaneously replace the sand head when the core making machine is to employ a different blow plate is that the distribution of openings in the freshly selected blow plate is or can be such that the previously used sand head and blow head cannot ensure adequate distribution of supplied sand to the openings so that the distribution of sand in the core box which is adjacent the freshly selected blow plate is unsatisfactory. If the total time which is taken up by a change of setup is between 10 and 40 minutes, a substantial part of such time is spent to separate the blow head from its carrier in order to gain access to the sand head. Moreover, it is customary to clean the sand head or an analogous sand supplying element on a daily basis. Each such cleaning operation must be preceded by detachment of the one-piece blow head from its carrier. This not only takes up much time but also necessitates repeated application and removal of fasteners which are used to separably connect the blow head to the carrier. Therefore, the useful life of such fasteners is relatively short. Moreover, and since the fasteners constitute or cooperate with means for centering the blow head on its carrier, the centering action invariably deteriorates with time as a result of extensive wear upon the fasteners and/or upon one or more centering elements which cooperate with the fasteners.